Public Class Form1
 
    Dim vA, vB, vC, vXstart, vXende, vXschritt As String
    Dim vX, vY As Double
 
    Dim vPCount As Integer = 0
    Dim vColor1 = Color.Red
    Dim vColor2 = Color.Blue
    Dim vColor3 = Color.Orange
    Dim vColor4 = Color.Brown
    Dim vColor5 = Color.Green
 
    Dim listGroups As ListViewGroup
    Dim listGroup As String
    Dim vNull1, vNull2 As Double
 
 
 
 
    Public Function TextBoxCheck() As Boolean
        Return txtAwert.Text.Length > 0 And txtBwert.Text.Length > 0 And _
          txtCwert.Text.Length > 0 And txtXstart.Text.Length > 0 And _
          txtXende.Text.Length > 0 And txtXschritte.Text.Length > 0
    End Function  'Button Auswerten durch txtBox aktivieren
 
    Private Sub linkParabel_LinkClicked(ByVal sender As System.Object, ByVal e _
      As System.Windows.Forms.LinkLabelLinkClickedEventArgs) Handles _
      linkParabel.LinkClicked
        MessageBox.Show("Beispiel: 4x² + 9x + 16" & vbCr & "a = 4   b = 9  c =" & _
        "16", "Beispiel", MessageBoxButtons.OK, MessageBoxIcon.Information)
    End Sub 'Messagebox Beispiel
 
    Private Sub txtAwert_TextChanged(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles txtAwert.TextChanged
        btnListfill.Enabled = TextBoxCheck()
        vA = txtAwert.Text
    End Sub 'Button Auswerten durch txtBox aktivieren
 
    Private Sub txtBwert_TextChanged(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles txtBwert.TextChanged
        btnListfill.Enabled = TextBoxCheck()
        vB = txtBwert.Text
    End Sub 'Button Auswerten durch txtBox aktivieren
 
    Private Sub txtCwert_TextChanged(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles txtCwert.TextChanged
        btnListfill.Enabled = TextBoxCheck()
        vC = txtCwert.Text
    End Sub 'Button Auswerten durch txtBox aktivieren
 
    Private Sub txtXstart_TextChanged(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles txtXstart.TextChanged
        btnListfill.Enabled = TextBoxCheck()
        vXstart = txtXstart.Text
    End Sub 'Button Auswerten durch txtBox aktivieren
 
    Private Sub txtXende_TextChanged(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles txtXende.TextChanged
        btnListfill.Enabled = TextBoxCheck()
        vXende = txtXende.Text
    End Sub 'Button Auswerten durch txtBox aktivieren
 
    Private Sub txtXschritte_TextChanged(ByVal sender As System.Object, ByVal e _
      As System.EventArgs) Handles txtXschritte.TextChanged
        btnListfill.Enabled = TextBoxCheck()
        vXschritt = txtXschritte.Text
    End Sub 'Button Auswerten durch txtBox aktivieren
 
 
 
    Private Sub btnListfill_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles btnListfill.Click
 
        vPCount = vPCount + 1
 
        listGroup = vA & "x² + " & vB & "x + " & vC
 
 
        vNull1 = -(vB / vA) / 2 + Math.Sqrt(Math.Pow((vB / vA) / 2, 2) - (vC / _
          vA))
        vNull2 = -(vB / vA) / 2 - Math.Sqrt(Math.Pow((vB / vA) / 2, 2) - (vC / _
        vA))
 
 
 
 
        If vPCount = 1 Then
            listParabel.Items.Add(listGroup).SubItems.Add(vNull1 & ", " & _
              vNull2)
            listParabel.Items.Item(vPCount - 1).ForeColor = vColor1
            Call parabellistfill()
        ElseIf vPCount = 2 Then
            listParabel.Items.Add(listGroup).SubItems.Add(vNull1 & ", " & _
              vNull2)
            listParabel.Items.Item(vPCount - 1).ForeColor = vColor2
            Call parabellistfill()
        ElseIf vPCount = 3 Then
            listParabel.Items.Add(listGroup).SubItems.Add(vNull1 & ", " & _
              vNull2)
            listParabel.Items.Item(vPCount - 1).ForeColor = vColor3
            Call parabellistfill()
        ElseIf vPCount = 4 Then
            listParabel.Items.Add(listGroup).SubItems.Add(vNull1 & ", " & _
              vNull2)
            listParabel.Items.Item(vPCount - 1).ForeColor = vColor4
            Call parabellistfill()
        ElseIf vPCount = 5 Then
            listParabel.Items.Add(listGroup).SubItems.Add(vNull1 & ", " & _
              vNull2)
            listParabel.Items.Item(vPCount - 1).ForeColor = vColor5
            Call parabellistfill()
        Else
            MessageBox.Show("Maximal 5 Parabeln!", "Halt!", _
              MessageBoxButtons.OK, MessageBoxIcon.Error)
        End If
 
 
 
 
    End Sub 'Liste auffüllen
    Public Sub parabellistfill()
        listGroups = New ListViewGroup(listGroup)
 
 
        listWerte.Groups.Add(listGroups)
 
        For vX As Integer = vXstart To vXende Step vXschritt
 
 
 
            vY = vA * vX * vX + vB * vX + vC
            listWerte.Items.Add(New ListViewItem(vX, listGroups)).SubItems.Add( _
              vY)
 
 
        Next
 
 
 
 
    End Sub